Among the themes of this SCCOR proposal, one that has played a major role in its development is the delineation of critical cardiac signaling pathways and identification, in the components of these pathways, of human genetic polymorphisms that modify the susceptibility to, or progression of, heart failure. Our group of investigators has applied a systematic vertically-integrated analysis for identifying novel polymorphisms in cardiac signaling and calcium-handling genes, defining associations with specific clinical features or outcomes, determining the functional effects of these polymorphisms using in vitro expression systems, and establishing the pathophysiological effects of these polymorphisms in intact biological systems, i.e. genetically manipulated mice and rabbits. Although associative and case-control human studies drive these investigations, and will clearly provide the biological framework for mechanistic studies, the development of suitable mouse models will permit experiments to be performed on individual gene variants that are simply not attainable with human subjects. To facilitate this vertical scientific approach, Core D will perform complex manipulations of the mouse genome in order to generate optimal mouse models for the SCCOR investigators'mechanistic studies, including conditional and conventional knock-outs, knock-ins, multi-gene substitutions, and targeted transgenesis. In support of the SCCOR projects, the Core will assist in the design of targeting strategies, will engineer targeting vectors, will electroporate, select for and identify targeted ES cells, and will perform blastocyst injection for generation of chimeric mice.